The Red Devils saw Tuesday night's game at Brentford called off after they were forced to close their Carrington training complex as a result of rising COVID-19 cases.
The Premier League has now confirmed that Saturday's contest at Old Trafford will also be postponed, as Man United are "unable to field a team" following "additional positive tests" on Thursday.
Saturday's game is the fourth to be postponed for COVID-related reasons this week, while Tottenham Hotspur's match against Brighton last weekend was also called off.
However, the Premier League has reiterated its intention to fulfil the current fixture schedule where possible, seemingly ruling out the prospect of a 'circuit-breaker' for the time being.
"Manchester United's fixture against Brighton & Hove Albion this weekend has been postponed by the Premier League Board today. It is with regret that this is the fourth Premier League fixture to have been postponed in the past week," read a statement from the Premier League.
"While recognising a number of clubs are experiencing COVID-19 outbreaks, it is the League's intention to continue its current fixture schedule where safely possible. The health and wellbeing of all concerned remains our priority.
"Regarding Manchester United's game on Saturday, the club continues to have an ongoing COVID-19 outbreak within their squad, which has left them unable to field a team for the match at Old Trafford.
"A significant number of COVID-19 cases led to their game against Brentford FC being called off earlier this week, and today additional positive tests have been confirmed."
Manchester United's next match is due to come away to Newcastle United on December 27 - 16 days after their last outing - while Brighton are scheduled to be back in action on December 26 against Brentford. body check tags ::